Railway bogie with improved stability and behavior in curves having a slidably mounted axle box arm

ABSTRACT

A railway vehicle truck includes axles (12) with shrunk-on wheels and journalled in axle-boxes (20) connected to a rigid frame (2,4) through a horizontal primary connection comprising a link (18) coupled to the side member (2) of the frame by a resilient swivel joint (14). At least one of the four axle-boxes (20) is longitudinally slidable on a carriage (36) relative to the side member (2). The sliding motions are controlled by a linkage (22,24,26,30) having its input member (22) connected to the body of the vehicle, or by a damper (34) and an automatic return disposed in parallel relation to each other. The device improves on the operation of trucks taking a curve.

BACKGROUND OF THE INVENTION

The invention relates to a truck for a railway vehicle which comprisesan adjustable frame having side members and two axles having shrunk-onwheels and journalled in axle boxes each connected to the frame througha primary suspension comprising a link having one end connected to theaxle-box and the other end connected to a side member of the framethrough a resilient swivel joint. Such trucks are for example the trucksX32 of the French CORAIL cars. The invention more particularly relatesto means for mounting at least one of the axle-boxes so as to allow it adegree of freedom of substantially horizontal relative motion withrespect to the frame.

Present railway technique has permitted the development of railwaytrucks having wheels shrunk on the axle spindles which conserve goodcharacteristics of stability up to speeds of 400 km/h and even beyond.Such trucks are based on the principle of a double suspension: a primarysuspension and a secondary suspension, these two suspensions beingseparated by an intermediate movable element between the axles and thebody of the vehicle designated truck frame.

It is known that the motions of instability at high speed (or biconicalmotions of undamped axles) can be suppressed in particular by highprimary stiffnesses of the primary suspension considered in thehorizontal plane.

Unfortunately, the stiffening of the horizontal flexible connectionswhich maintain the axle-boxes relative to the truck frame has resultedin the concerned trucks badly taking the curves, i.e. the axles becomedecentered relative to the two rail lines and the wheel flanges come toabut against the outer rail of the curve, especially the wheel of thefront axle of each truck.

A drawback of this phenomenon is that the contact of the wheel flangesresults in both wear on the wheel flanges themselves and wear on therolling surfaces of the wheels. A second drawback is that, in a curve,the axles effected by the contact between the flange and outer railfollows the defects on the inner rounded portion of the rail on whichthe contact occurs and the suspension transmits undesirable forces tothe body.

The adoption of the greasing of the wheel flanges or the rails in acurve permits combatting the first drawback but not the second. Aconcern of designers is therefore to propose a solution for correctlypositioning the axles with respect to the track, even in a curved track,with the centers of the axle-boxes located at the four corners of arectangle.

Thus, in order to improve the passage through a curve a certain numberof specialists have proposed mechanical link systems employing therelative rotational motion of the equipment constituted by the two axlesof a truck (or even of each axle of rolling stock with merely axles)relative to the body placed vertically thereabove. These link systemshave the purpose of modifying the relative disposition of the axle-boxeswith respect to one another as a function of the curve radius so as toobtain in a curve a truck geometry which is more favorable to its takingthe curve.

But the systems proposed at present above all aim to create in anestablished curve a geometry favorable to the truck considered in thefree state, i.e. without taking into account semi-slip forces whichoccur in the contact between the wheels and the rails.

In a certain number of proposed solutions, the position of equilibriumcannot be attained, even if the geometry of the wheels obtained in acurve by a "forced" motion corresponds to a truck which takes theconsidered curve well, quite simply because the proposed truck is notmorphologically designed for an automatic seeking of a correctpositioning of the axles with respect to the track. Thus, for example,it is not sufficient to make the axes of two axles of a truck convergein the correct direction for them to make an angle equal to the angle atthe center from which is seen, from the center of the considered curve,a segment equal to the wheelbase of the truck so that this truck behaveswell in the considered curve. In failing to take certain constructionalprecautions, the detail of which constitutes a characteristic of thepresent invention and will be explained hereinafter, there is a riskthat a truck according to the aforementioned example will place itselfacross the curved track and advance crabwise.

There are, for example, known from the patent documents German DE-A-3424 531 or European EP-A-165 752, trucks of the type mentioned at thebeginning of this description, provided with means for mounting theaxle-boxes adapted to enable the axles to assume in a curve a certaininclination relative to the longitudinal axis of the frame. But thesemeans, arranged in parallel with the primary suspension, consist oflinkages which fix in position at least two axle-boxes. The primarysuspensions are necessarily rendered more flexible and the linkageexerts on the boxes high stresses transmitted by numerous link memberswhich are fragile and liable to result in play, which is thereforeunsatisfactory.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to improve the behavior in a curveof trucks suitable for high speeds whose stability in yaw was obtainedby a suitable stiffening of the primary suspension mechanicalconnections in the horizontal plane (stiffnesses conventionallydesignated by the gradients Kx and Ky). This is the case in particularin France of the Y32 equipping the CORAIL cars, the TGV trucks, and theFrench turbotrain trucks, etc.

It is known that the two axles of such trucks each undergo on astraight-line track coupled transverse and angular motions (about thevertical axis) in damped sinusoids, termed biconical motions or yawmotions, the damped position being a position of equilibrium orrelaxation of the horizontal stresses, both internal stresses whosesource is in the forces of contact between the wheels and the rail andthose, highly attractive, generated by the deviations assumed by thefour axle-boxes relative to the four centers of attraction correspondingto the horizontal primary resilient connections (according to theaforementioned gradients Kx and Ky). With regard to a well-constructedtruck, this position of relaxation corresponds to centers of attractiondisposed at the corners of a horizontal rectangle and it is therefore inaccordance with this geometrical figure that the centers of theaxle-boxes come to be disposed when the truck travels along arectilinear and perfect track, i.e. without natural defects of geometry.

If it is considered that the rectilinear track section has onlylocalized geometrical perturbations, the damped biconical motion isstarted up again for each perturbation, the damping moreover being lessand less effective as the speed of the vehicle approaches the speed ofinstability owing to the harmful effect of the forces of inertiarelating to the moving elements involved in the motion.

The present invention is based on the principle, supported bycalculations not reproduced here, that for given horizontal primarystiffnesses, conventionally expressed by the coefficients Kx(longitudinally) and Ky (transversely), the motion is substantially ofthe same type as that described hereinbefore about the position ofequilibrium, i.e. that the axles automatically seek their position ofequilibrium; it being however necessary that the latter be compatiblewith the play existing for each axle within the rails. A characteristicof the invention consists in deforming in a curve the aforementionedrectangular disposition of the primary attraction centers by thedisplacement or traversing of at least one of the centers of attractionrelative to the rectangle, whereas according to the technique known fromthe above documents DE-A-74 24 531 or EP-A-165 752, the axles were fixedwithout however displacing the centers of attraction which remainedlocated at the corners of a rectangle (which explains the stressesexisting in this type of connection).

In respect of the curve of smallest radius to be negotiated andtherefore corresponding to a maximum deformation of the rectangle, itwill be shown that the figure of equilibrium of the axles (if not ofrelaxation) is such that none of the flanges comes in contact with therail. The exact determination of the traversing to be effected dependson the geometric and mechanical data of the problem in question.

This calculation, which is not developed here, involves theaforementioned primary stiffnesses as well as--although to a lesserextent--the horizontal stiffnesses of the secondary suspension, theKALKER coefficients of wheel-rail contact--essentially the twocoefficients of longitudinal and transverse semi-slip--and the profileof the tires.

In practice, an approximate value of the amplitude of the traversingcorresponds to the convergence toward the center of the curve of the twonon-parallel sides of the trapezium obtained from the aforementionedrectangle by the traversing. From the point of view of the construction,to permit the displacement of the centers of attraction, the inventionis characterized in that the means for mounting the axle-boxes ensuringthe longitudinal selective freedom are interposed, in respect of eachbox concerned, between the link and either the axle-box, or the sidemember of the frame. In other words, the mounting is achieved in serieswith the primary suspension and no longer in parallel therewith.

According to the invention, it is possible not only to traverse, as justmentioned one, two, three or four primary centers of attraction of atruck, but also to achieve this traversing along substantially anycurve, the amplitude of the motion itself as a function of the curvepossibly satisfying a function which is itself any function to bedetermined by calculation. The sole limitations to be respected are toeffect the traversing motions in such manner as to respect thecoplanarity of the four centers and the stress limits imposed by thecomponent parts involved (swivel joints, axle rolling bearings, fatiguelimit of the axle spindles, etc.).

In a first embodiment, said mounting means comprise a carriage which isarranged to be longitudinally slidable on the side member and on whichis carried the resilient swivel joint of the link, control means beingprovided for controlling the sliding motions of the carriage withrespect to the side member.

Advantageously, a single one of the resilient swivel joints has itstransverse pin carried by a sliding carriage, the other three resilientswivel joints having their transverse pins rigidly connected relative tothe corresponding side member.

In a first possibility, the means for controlling the sliding motions ofthe carriage with respect to the side member are constituted by alinkage mounted between the body of the vehicle and said carriage, thepivotings of the body relative to the truck controlling thedisplacements of the carriage in a manner proportional to the angle ofrotation about the vertical axis between the body and the truck frame.

In a variant of the invention, it is not even necessary to modify bymeans of a mechanical control the position of the primary centers ofattraction. The modification of the position of the centers is obtainedby the axles themselves, the latter constituting the elements which areboth the driving elements and the controlling elements of the carriagescarrying the centers. The constructional dispositions required thenconsist in constraining the motion of the carriage(s) by two actionswhich act in a parallel manner and consist, one, in braking the motionsof the carriages by means of very powerful dampers, and, the other, increating a resilient return of the carriage to a mean position. Thefirst of these actions, which damps the rapid and pulsatory motionswhich would occur without this action, does not prevent the dampedbiconical motion of the axles from occurring and, in particular, theautomatic seeking on behalf of the axles of their position ofequilibrium both in a straight line and in a curve. On the other hand,the high damping action prevents the motions of instability which appearat high speeds from occurring. The second of the aforementioned actions,which is a resilient return action, is adapted to balance the tractionor braking forces.

Such an arrangement is particularly well applicable in a secondembodiment of the invention in which the relative freedom mounting meansare provided between the link and the axle-box.

In an advantageous embodiment of the variant of the invention, thisresilient return of the axle-box to its mean position is achieved by aneffect of gravity, but it must be understood that this resilient returnmay also be obtained by means of a spring having sufficient dimensionsto be capable of opposing the forces developed on the rim.

Advantageously, both the desired longitudinal motion and the return bythe effect of gravity are obtained by means of a mounting in theaxle-box of smooth bearings having an axis which is eccentric relativeto the axis of the axle.

The damper is fixed, preferably substantially vertically, between theattachment journals respectively connected to the axle-box and the link.

According to yet another variant, the link end comprises, adjacent tothe axle, a bore in which the axle-box rolls, it being maintainedtherein by one or more centering studs disposed on the upper generatrixof the aforementioned bore.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will be apparent fromthe following detailed description of a particular embodiment withreference to the accompanying drawings wherein:

FIG. 1 is a bottom plan view of a truck frame to which the invention isapplied;

FIG. 2 is a bottom plan view of the truck frame, showing the principleof the orientation explained hereinbefore, applied to a single axle-boxof a truck, the motion of the carriage being a motion of rectilinear andlongitudinal translation, the amplitude being moreover substantiallyproportional to the curvature of the track;

FIG. 3 is an elevational view, partly in cross section, of a furtherembodiment of the invention, showing the detail of the means formounting the axle-box according to the invention; and

FIG. 4 is a view similar to FIG. 3 showing another manner of achievingthe connections between the truck frame and the axle box according tothe invention.

DETAILED DESCRIPTION

With reference to FIG. 1, there is seen a truck frame constituted by twoside members 2 interconnected by cross-members 4. The secondarysuspension, not shown, bears against circular enlarged portions 6 of theframe side members. The driving of the body is achieved in aconventional manner through a swing bar 8 which is journalled on a bodypivot and connected at its ends to the cross-members 4 through bars 10.

The primary connections between the axles 12 and the truck frame areachieved also in a conventional manner through four resilient swiveljoints 14 whose transverse axes 16 are rigidly maintained with respectto the side members 2. These swivel joints resiliently maintain the axlebearings by means of four axle-box links 18 connected to the axle-boxes20 so that, in the absence of horizontal forces exerted on theaxle-boxes, the centers of the latter are located at the corners of arectangle.

In FIG. 2 which represents a device according to the invention and isderived from the conventional arrangement represented in FIG. 1, one ofthe four swivel joints, namely that placed on the top left side of theFigure, disposed inside a carriage or slide 36, is longitudinallyslidable in slideways connected to the upper branch of the side member2, located on the left side of the Figure. The motion of very smallamplitude (on the order of a centimeter) from a mean position, isproduced by the motion of relative rotation between the body and thetruck owing to a lever 22 connected to the body substantially at thesame height dimension as the driving swing bar or the axes of the axles.It is rigidly fixed, for example, to the body pivot and actuates alongitudinal connector 24, then a transverse lever 26 journalled on apin 28 fixed relative to the side member 2, and lastly a longitudinalconnector 30 which drives the slide in which the swivel joint 14 ismounted.

The articulations 32 of the various connectors and swing bars mentionedhave only a minimum of play and may possibly receive flexible linings,but in the latter case, the flexibility of these linings must notsubstantially modify the desired flexibility on the axle-box in questionwhich is that given by the swivel joint 14.

According to the variant of the invention, the primary connection of atleast one of the axle-boxes 20 comprises, interposed between the link 18and the considered box 20, mounting means, the detail of which is givenin FIG. 3, which allows a horizontal relative motion between thelink--and consequently the frame--and the axle-box 20.

The box link 18 comprises, adjacent to the axle, a seat 45 in its upperpart for receiving and centering the primary suspension spring 41provided for the considered axle-box 20 and supporting, in aconventional manner not shown, an end of a side member 2 of the truckframe.

Further, the box link 18 maintains, the axle-box 20 by means of twovertical cheeks 42 which also constitute smooth bearings the bore axisof which, represented by the point 0, is eccentric relative to the axisof the axle 12 represented by the point C in FIG. 3. The eccentricity istypically about 3 to 5 cm.

In the absence of a propelling or braking force, the center C of theaxle 12 is located vertically above the center 0 of the eccentricbearing of the axle-box.

On the other hand, under the effect of propelling or braking forces, thesegment CO assumes an inclination to the vertical, which provides thenecessary longitudinal motion (on the order of a centimeter forexample). The axle 12 is then returned to its original position underthe effect of gravity by a return force which is a function of thevertical weight exerted on the axle-box 20 in question, of theeccentricity CO and of the displacement of the axle-box 20 relative toits original position or mean position.

Further, the box body 20 comprises, on a suitable projection, a lowerattachment 43 of the damper 34, the upper attachment 44 being fixed tothe box link 18. These two attachments 43 and 44 are constituted byjournals.

It will be observed that FIG. 3 represents a damper whose axis is nearlyvertical. Such an arrangement, without being obligatory, provides aprotection against risks of leakage of the damper, the latter being thenimmersed in the conventional manner in an oil reservoir which performsthe function of a feeder for re-feeding the damper.

Lastly, note that the use of viscous dampers permits attaining aquasi-total relaxation of the forces at the rim in an establishedcondition of operation either in a straight line or in an establishedcurve. But it is also possible to employ friction dampers. In this case,residual forces subsist even in an established condition of operation.On the other hand, such friction dampers involve no risk of leakage ofliquid and consequently afford maximum operational safety.

In FIG. 4, the longitudinal mobility of the axle-box 20 with respect tothe box link 18 is achieved by a slip-free rolling of the axle-box 20 ina transverse bore formed in the box link adjacent to the axle. The axisof this bore corresponds to the trace C in the section plane of FIG. 4.The slip-free rolling of the axle-box in the aforementioned bore isachieved by means of one or more centering studs 46 engaged between thebox link and the body of the axle-box and placed on the contactgeneratrix of these two component parts. The fact of providing aplurality of centering studs permits preventing the axle-box and thebore from becoming off-center which is liable to occur under the effectof transverse forces.

The arrangement shown in FIG. 4 has the advantage of greatly reducingthe effect of the dry frictions.

We claim:
 1. In a truck for a railway vehicle body running on a trackincluding a rigid frame having side members and two axles journalled inaxle-boxes and shrunk-on wheels on the axles, the axle-boxes each beingconnected to the frame through a respective primary suspension linkhaving one end connected to the axle-box and the other end articulatedto a respective one of said side members of the frame through aresilient swivel joint, the swivel joint being sufficiently stiff fordamping yaw motions of the truck at the highest speeds encountered inthe use thereof, the improvement comprising:carriage means mountedbetween at least one of said axle-boxes and said frame on saidrespective one of said side members for horizontal and longitudinalsliding movement thereon, one of said resilient swivel joints of saidlink being mounted on said carriage means; and controls means forsliding said carriage means relative to said respective one of said sidemembers as a function of the radius of curvature of the track.
 2. Thetruck as claimed in claim 1, wherein:said control means compriseslinkage means operatively connected between the vehicle body, the frameand said carriage means, so that pivoting of the body relative to thetruck controls displacements of said carriage.
 3. In a truck for arailway vehicle body running on a track including a rigid frame havingside members and two axles journalled in axle-boxes and shrunk-on wheelson the axles, each axle-box being connected to the frame through arespective primary suspension link having one end connected to theaxle-box and the other end articulated to a respective one of said sidemembers of the frame through a resilient swivel joint, the swivel jointbeing sufficiently stiff for damping yaw motions of the truck at thehighest speeds encountered in the use thereof, the improvementcomprising:mounting means for mounting at least one of said axle-boxeson a respective one of said primary suspension links for relativelongitudinal displacement substantially parallel to the direction oftravel of the truck so that at least one of said axle-boxes isautomatically returnable to a position of equilibrium thereof, saidmounting means comprising a rotatable connection means between said atleast one of said axle-boxes and said respective one of said links forrelative rotation therebetween about an axis eccentric to the centralaxis of rotation of the axle journalled in said at least one of saidaxle-boxes; and damper means mounted between said at least one of saidaxle-boxes and said respective one of said primary suspension links fordamping said relative longitudinal displacement.
 4. The truck as claimedin claim 3 wherein:said damper means is disposed so that the actionthereof is substantially vertical.
 5. The truck as claimed in claim 4wherein:a substantially radially extending arm is provided on said atleast one axle-box; and said damper means comprises a substantiallylinear acting damper device connected between said arm and said onelink.
 6. In a truck for a railway vehicle body running on a trackincluding a rigid frame having side members and two axles journalled inaxle-boxes and shrunk-on wheels on the axles, each axle-box beingconnected to the frame through a respective primary suspension linkhaving one end connected to the axle-box and the other end articulatedto a respective one of said side members of the frame through aresilient swivel joint, the swivel joint being sufficiently stiff fordamping yaw motions of the truck at the highest speeds encountered inthe use thereof, the improvement comprising:mounting means for mountingat least one of said axle-boxes on a respective one of said primarysuspension links for relative longitudinal displacement substantiallyparallel to the direction of travel of the truck so that said at leastone of said axle-boxes is automatically returnable to a position ofequilibrium thereof, said mounting means comprising,a curved internalbearing surface in said respective one of said suspension links andhaving a central axis eccentric relative to the central axis of rotationof the axle journalled in said at least one of said axle-boxes, a curvedexternal bearing surface on said at least one of said axle-boxes inrolling contacting engagement with said curved internal bearing surface;and damper means mounted between said at least one of said axle-boxesand said respective one of said primary suspension links for dampingsaid relative longitudinal displacement.
 7. The truck as claimed inclaim 6 wherein:said curved internal bearing surface is in one end ofsaid one link; and said axle-box is automatically returnable by gravity.8. The truck as claimed in claim 7 and further comprising:a centeringstud means engaging between said curved bearing surfaces to preventslipping therebetween while permitting said rolling contact.
 9. Thetruck as claimed in claim 8 wherein:said damper means is disposed sothat the action thereof is substantially vertical.
 10. The truck asclaimed in claim 9 wherein:a substantially radially extending arm isprovided on said at least one axle-box; and said damper means comprisesa substantially linear acting damper device connected between said armand said one link.
 11. The truck as claimed in claim 7 wherein:saiddamper means is disposed so that the action thereof is substantiallyvertical.
 12. The truck as claimed in claim 8 wherein:a substantiallyradially extending arm is provided on said at least one axle-box; andsaid damper means comprises a substantially linear acting damper deviceconnected between said arm and said one link.
 13. The truck as claimedin claim 6 wherein:said damper means is disposed so that the actionthereof is substantially vertical.
 14. The truck as claimed in claim 6wherein:a substantially radially extending arm is provided on said atleast one axle-box; and said damper means comprises a substantiallylinear acting damper device connected between said arm and said onelink.